A simplified diagrammatic representation of a disk drive, generally designated as 10, is illustrated in FIG. 1. The disk drive 10 includes a disk stack 12 (illustrated as a single disk in FIG. 1) that is rotated by a spindle motor 14. The spindle motor 14 is mounted to a base plate 16. An actuator arm assembly 18 is also mounted to the base plate 16.
The actuator arm assembly 18 includes a transducer 20 (or head) mounted to a flexure arm 22 which is attached to an actuator arm 24 that can rotate about a pivot bearing assembly 26. The actuator arm assembly 18 also includes a voice coil motor 28 which moves the transducer 20 relative to the disk 12. The spin motor 14, and actuator arm assembly 18 are coupled to a number of electronic circuits 30 mounted to a printed circuit board 32. The electronic circuits 30 typically include a digital signal processor (DSP), a microprocessor-based controller and a random access memory (RAM) device.
Referring now to the illustration of FIG. 2, the disk stack 12 typically includes a plurality of data storage disks 34, each of which may have a pair of disk surfaces 36, 36. The disks 34 are mounted on a cylindrical shaft and are designed to rotate about axis 38. The spindle motor 14 as mentioned above, rotates the disk stack 12. Although the disks 34 are described as magnetic disks for purposes of illustration, they may alternatively be optical disks or any other type of storage disk which can store data thereon.
Referring now to the illustration of FIGS. 1 and 3, the actuator arm assembly 18 includes a plurality of the transducers 20, each of which correspond to one of the disk surfaces 36. Each transducer 20 is mounted to a corresponding flexure arm 22 which is attached to a corresponding portion of the actuator arm 24 that can rotate about the pivot bearing assembly 26. The VCM 28 operates to move the actuator arm 24, and thus moves the transducers 20 relative to their respective disk surfaces 36. The transducers 20 are configured to fly adjacent to the disk surfaces 36 on air bearings.
Although the disk stack 12 is illustrated as having a plurality of disks 34, it may instead contain a single disk 34, with the actuator arm assembly 18 having a corresponding single actuator arm 24.
FIG. 4 further illustrates one of the disks 34. Data is stored on the disk 34 within a number of concentric tracks 40 (or cylinders). Each track is divided into a plurality of radially extending sectors 42 on the disk 34. Each sector 42 is further divided into a servo sector 44 and a data sector 46. The servo sectors 44 of the disk 34 are used to, among other things, accurately position the transducer 20 so that data can be properly written onto and read from the disk 34. The data sectors 46 are where non-servo related data (i.e., user data) is stored and retrieved. Such data, upon proper conditions, may be overwritten.
To accurately write data to and read data from the data sectors 46 of the disk 34, it is desirable to maintain the transducer 20 at a relatively fixed position with respect to a centerline of a designated track 40 during writing and reading operations (called a track following operation). To assist in controlling the position of the transducer 20 relative to the tracks 40, the servo sectors 44 contain, among other things, servo information in the form of servo burst patterns that include one or more groups of servo bursts, as is well-known in the art.
Various characteristics that are associated with the disk drive 10 can affect its ability to accurately write data on the disk 34. For example, air density can affect the flying height of the transducer 20 over the disk 34, dust/debris on the disk 34 can affect the sensitivity of the communicative coupling between the transducer 20 and the disk 34, and temperature can affect the reliability and operation of various components of the disk drive 10.